FIG. 1 is a perspective view of an opening portion of a conventional can. As shown in the figure, contents such as beverage or beer to be drunk are generally contained within a can body 10, and an opening device for opening the can is generally attached to a top surface 12 or bottom surface of the can body. An opening member 20 attached to the top surface 12 through a rivet stub 24 is used to open a predetermined portion of the top surface of the can body 10. Further, the opening member 20 comprises a grip 22 extending to one side with respect to the rivet stub 24, and a pressing portion 26 extending to the opposite side with respect to the rivet stub 24.
An opening portion 29 defined by an incision line 28 grooved with a predetermined depth is formed on a portion of the top surface 12 below the pressing portion 26.
Here, when a user pulls up the grip 22, the pressing portion 26 of the opening member 20 opposite to the grip 22 is moved downward around the rivet stub 24. When the pressing portion 26 is moved downward, a downward force is applied to the opening portion 29, and the opening portion 29 is then substantially separated from the top surface 12 along the incision line 28 for defining the opening portion 29. With this action, the opening portion 29 is substantially opened so that the beverage of the can body 10 may flow out.
A portion of the opening portion 29 defined by the incision line 28 is still attached to the top surface 12 of the can body. Thus, it is also known in the art that when the can is opened as the opening portion 29 is moved downward by the pressing portion 26, the portion of the opening portion 29 is constructed to be still attached to the top surface 12 of the can.
However, there are the following problems in the prior art. That is, when the beverage flows out from the interior of the can body 10, exterior air should be introduced to the interior of the can body 10 to the contrary so that the beverage may smoothly flow out. However, in the constitution of the can according to the prior art, since only one opening portion 29 is formed, there is a disadvantage in that the contents cannot smoothly flow out in a process of introduction of the exterior air and simultaneous outflow of the beverage. Accordingly, in an initial stage until a predetermined amount of beverage substantially flows out from the can (i.e., until the exterior air is introduced through an upper part of a hole corresponding to the opening portion while the beverage flows out through a lower part of the hole by tilting the can at a certain angle), it is very difficult to drain the beverage.
Next, a type of opening device for the conventional can will be described with reference to FIGS. 3 and 4. The type of opening device shown in FIG. 3 is a so-called ring-pull-tab type, wherein when a grip 62 of a tab 60 installed on a top surface U of the can is pulled up, an opening portion 64 is lifted together with a rivet stub. That is, the opening portion 64 is opened while being lifted as the tab 60 moves upward. In this case, the opening portion 64 defined by an incision line 64a is completely separated, together with the tab 60, from the top surface U of the can. In such a type, it can be seen that the rivet stub 66 is installed substantially within the opening portion 64.
Such a ring-pull-tab type opening device has an advantage in that an opening force applied by a user is smaller, but has a disadvantage in that it is environmentally undesirable since both the tab 60 and the opening portion 64 are separated from the top surface U of the can.
FIG. 4 shows a so-called stay-on-tab type opening device. In such an opening device, when a grip 72 of a tab 70 installed on a top surface U of a can is pulled up, a pressing portion 76 moves downward around a rivet stub 74 and presses an opening portion 78 therebelow. Therefore, the opening portion 78 is urged downward and then spaced apart from the top surface U so that the opening portion 78 may be substantially opened. In such a stay-on-tab type opening device, it can be seen that the rivet stub 74 is installed on a portion of the top surface U outside of the opening portion 78.
In this opening device, the entire opening portion 78 is not opened but a portion of the opening portion 78 is still attached to the top surface U of the can. Therefore, such an opening device is advantageous to environmental protection since the opening portion 78 is not separated from the top surface U of the can, but has a disadvantage in that a force required for lifting the tab 70 through the grip 72 is larger than that of the ring-pull-tab type opening device.
In order to overcome these disadvantages of the opening devices for the cans each of which has a single opening portion, an opening device for a can shown in FIG. 2 has been proposed in Korean Utility Model Laid-Open Publication No. 98-55776 and Japanese Utility Model Laid-Open Publication No. (Sho) 55-69029. This opening device will be described in brief with reference to FIG. 2.
As shown in the figure, the conventional opening device for a can comprises a pair of opening portions 32 and 34 formed on a top surface of the can. The opening portions 32 and 34 are defined by incision lines where the top surface of the can is processed to be relatively thin in thickness when they are manufactured by a metallic pattern. Such opening portions 32 and 34 are composed of a first opening portion 32 through which contents of the can are able to substantially flow out to the outside upon opening thereof, and a second opening portion 34 through which exterior air is able to be introduced into the can upon opening thereof.
The opening device includes a grip 30 which a user can catch with his/her finger(s), and a pair of pressing portions 36a and 36b formed at both ends of the grip for pressing and opening the opening portions 32 and 34, respectively. Here, when the user pulls up the grip 30, the pressing portions 36a and 36b press the opening portions 32 and 34 downward around lever fulcrums Ha and Hb, respectively. The opening portions 32 and 34 are then spaced apart downward from the top surface of the can so that the contents may flow out.
According to the conventional opening device constructed as such, the contents may more easily flow out to the outside by forming substantially two opening portions. Further, in a case where the opening portions are formed into a pair, the two opening portions should be opened when the grip 30 is pulled up. Therefore, the opening portions should be more easily opened by means of a force with which a user pulls up the grip.
However, according to the conventional opening device shown in the figure, it is not easy to substantially simultaneously open the two opening portions. That is, since the grip should be pulled up with a force larger than that required for a conventional opening device for opening a single opening portion, there is naturally inconvenience of use. Further, since sufficient strength resistant to such a larger force should be ensured between the grip and the pressing portions, there is a disadvantage in that there are limitations on the design thereof in view of strength.